<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            height: 400px;
            width: 400px;
            position: relative;
            background-color: red;
            transform: rotate(45deg);
            left: 300px;
            top: 300px;
            box-shadow: 0px 0px 50pxred;
            animation: changel 1s infinite alternate-reverse;
        }

        .box::after,
        .box::before {
            display: block;
            position: absolute;
            content: "";
            height: 400px;
            width: 400px;
            background-color: red;
            /* transform:rotate(45deg);*/
            border-radius: 50%;
            box-shadow: 0px 0px 50px red;
            /* 周一讲 */
            background-image: radial-gradient(199px at 8px 129px， rgb(255 117 117)0%， 口red 100%);
        }

        .box::after {
            left: -200px;
        }

        .box::before {
            top: -200px;
        }

        .big {
            height: 400px;
            width: 400px;
            /* 周一讲
alternate-reverse 重复播放
infinite 无限次数
*/
            animation: change 500ms alternate-reverse infinite;
        }

        @keyframes changel {
            0% {
                box-shadow: 0px 0px 10pxred;
            }

            100% {
                box-shadow: 0px 0px 20pxred;
            }
        }

        @keyframes change {
            0% {
                /* 缩小0.8倍 */
                transform: scale(0.8);
            }

            100% {
                transform: scale(1);
            }
        }
    </style>
</head>

<body>
    <div class="big">
        <div class="box"></div>
    </div>
</body>

</html>